1. Technical Field
Method with minimal sensor requirements to control ignition timing for internal combustion engines or injection timing for diesel engines, as well as for optimizing fuel injection quantities.
Most ignition systems are predictive, approximating the time from ignition to combustion (“ignition time”) with stored test engine parameters. By contrast, this invention uses one sensor measuring directly or indirectly the “ignition time” in real time, where the measuring can also be used for fuel quantity optimization. Therefore, fewer sensors are needed in general and in particular when fuel types are mixed (petrol, ethanol, gas or diesel and bio-fuel). Cost to produce an automotive engine management system can be reduced, while the system reliability increases. Fuel consumption is reduced, since the engine runs optimally under more combinations of external parameters (humidity, air pressure, air and engine temperature, fuel quality and mix, wear and tear, etc.).
2. Description of Related Art
This invention concerns a method to operate an internal combustion engine as well as an internal combustion engine, which operates in accordance with the method described in this invention.
When operating an internal combustion engine, it is often necessary to control the point where combustion commences. Since there is a delay between fuel ignition (firing spark plugs or injecting diesel) and start of (full) combustion, an ignition control system must start the ignition process a certain amount of time ahead of a reference point, where the amount of time depends on the time needed for the fuel to ignite.
To compute optimal timing and fuel dosage parameters, traditionally, a predictive approach is used, where in a test laboratory/test field setting; engines are subjected to different environment and load situations. Such test field results are then stored in an appropriate form, mostly electronically (ROM) or mechanically (spring). During engine operation, the stored parameters together with proxy sensors are used to predict the ignition time or the injection time. However, most of these methods try to predict or estimate parameters, which are at least to some degree, based on the environment during the laboratory trials. Wear and tear or unusual combinations of circumstances can only partially be accommodated. Also, changes in fuel mixtures (addition of bio fuels, ethanol, gas, etc) and changes in fuel quality can only be accommodated for in approximate terms.
EP 0 810 362 D2 discloses a method to estimate and control the combustion rate with discrete measurements of cylinder pressure. Combustion rate is controlled by a combination of varying fuel amounts and ignition timing. Adaptive ignition by contrast does not use cylinder pressure or estimates of combustion rates, but measures the SOC point using a continuous sensor reading. Further, adaptive ignition does not use fuel quantities to control ignition timing and more importantly, adaptive ignition controls ignition timing, not combustion rate.
EP 1 777 398 A2 discloses an invention to control a variable valve actuation system using cylinder pressure as input in an auto ignition application. Cylinder pressure is not used by adaptive ignition, nor is adaptive ignition intended for valve timing control. Further, adaptive ignition is not restricted in its application to auto ignition, as it can be used for conventional (petrol) as well as auto ignition (diesel) engines.
EP 1 164 277 A2 discloses a method to control auto ignition for pre-mixed fuel (multi injection, etc.), to some degree applying predictive (table lookup) rather than adaptive algorithms. Main variable is calculated heat release deduced from cylinder pressure. By contrast, adaptive ignition does not use cylinder pressure and is not restricted to the very specific application of auto ignition using petrol.
DE 195 13 307 AI discloses a process to determine type of fuel used (heavy or light quality), using cylinder pressure as input. Uses total time of combustion to deduce which fuel type is in use, by analyzing cylinder pressure. Adaptive ignition adapts to different fuel types, but does otherwise not try to recognize fuel types and more importantly, adaptive ignition does not use cylinder pressure.
Patent DE 103 30 819 B4 deals with a method to obtain a homogenous combustion and minimising the amount of particles by measuring light emitted at very specific wavelengths. The AI (adaptive ignition) patent has as its main purpose not the homogeneity of a combustion or particle reduction, but aims to determine the optimum time to commence firing spark plugs (petrol application) or injecting fuel (diesel application). Adaptive ignition is also not restricted to the use of optical sensors. However, when using optical sensors, it does not evaluate specific wavelengths, but the integral of all light emitted.
DE 103 07 367 A 1 deals with a method to control engines fueled with gas, where the cylinder pressure is measured and analysed. The principal aim is to control the fuel (gas) quantity, although no specific algorithm is mentioned. Further, there are unspecific provisions to influence ignition timing, based on the analysis of cylinder pressure curves. Adaptive ignition on the contrary has as its main goal a precise control of the point where spark plugs are to be fired, or diesel is to be injected. Further, adaptive ignition is not restricted to the use of gas as fuel and does not use cylinder pressure, nor does it operate by analysing pressure curves.
DE 25 13 289 AI deals only with diagnostics in a laboratory setting, not a real time method.
DE 697 35 846 T2 discloses a method which only applies to diesel engines (pressure ignition) with pre-mixed fuel in the cylinder. The ignition timing is not controlled by the injection timing of primary fuel (or firing of spark plugs) Timing of the injection of the secondary fuel is not linked to a sensor measurement, but only broadly linked to an electronic control unit. The means to control the ignition timing are also the quantity of a secondary fuel injection, as well as a variable compression ratio, rather than the timing (as in adaptive ignition) of the fuel injection (or firing of spark plugs).
WO 2006/053438 AI uses a bearing mounted accelerometer as proxy of cylinder pressure, to determine combustion quality, predominantly for premixed fuel applications. Adaptive ignition does not use cylinder pressure and is not restricted to auto (self) ignition.
US 2005/0072402 deals with pre-mixed charge auto (self) ignition, using proxies of cylinder pressure. Adaptive ignition does not use cylinder pressure and is not restricted to the specific application of multi injection/pre-mixed charge, auto ignition.
Winkelhoffer E. et al, MTZ journal September 2001; Optical combustion diagnostik, Issue 62 pages 644-651, concerns itself with analysis in a laboratory setting, not applicable for production engines and real time adjustment of engine parameters. Principal aim is also the detection of causes for knocking, as well as homogeneity of combustion, rather than the very specific (adaptive ignition) task of controlling engine parameters in real time.
Spicher U., MTZ journal April 2007, 3D optical sensors, Issue 68, pages 294-301, deals with a scientific approach to analyse the propagation of flame fronts. Not a method which can be applied to real time optimisation of engine parameters.